It is said that α-fetoprotein (AFT) (LCA-binding AFP) that binds to lentil lectin (LCA) increases in biological samples when hepatitis/liver cirrhosis changes to liver cancer. An antibody for detecting LCA-binding AFP is described in JP S63-307900 A. It is described that the antibody of JP S63-307900 A shows reactivity to the binding AFP and shows no reactivity with LCA non-binding AFP.
In JP S63-307900 A, it is described that fucose exists in the sugar chain of AFP to which LCA binds. The fraction of AFP that binds to lentil lectin in a biological sample is called AFP-L3 fraction. The AFP-L3 fraction is composed of fucosylated AFP (AFP in which core fucose (fucose which is bound in α-1,6 linkage to N-acetylglucosamine (GlcNAc) at the reducing end of N-type sugar chain) is added to the asparagine residue of AFP).
In the examples of JP S63-307900 A, antibodies which bind to LCA-binding AFP (AFP-LCA-R) and do not bind to LCA non-binding AFP (AFP-LCA-NR) have been acquired (see Example 1, FIG. 7, FIG. 1). However, the epitope of this antibody is unknown. In the examples, LCA-binding and non-binding properties are said to be caused by the presence or absence of fucose as described above, and the binding affinity to antigen may depend on the fucose moiety independent of the sequence of the peptide moiety. In that case, the antibody may non-specifically bind not only to AFP but also to proteins having other fucose. Therefore, development of a monoclonal antibody having epitope on both the fucose portion of the glycopeptide and the amino acid of the peptide portion is desired.